Differential mechanisms of binding of anti-sigma factors Escherichia coli Rsd and bacteriophage T4 AsiA to E-coli RNA polymerase lead to diverse physiological consequences
Differential mechanisms of binding of anti-sigma factors Escherichia coli Rsd and bacteriophage T4 AsiA to E-coli RNA polymerase lead to diverse physiological consequences
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DOI：
10.1128/jb.01792-07
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发表时间：
2008-05-01
影响因子：
3.2
通讯作者：
Chatterji, Dipankar
中科院分区：
文献类型：
--
作者：
Sharma, Umender K.;Chatterji, Dipankar
抗西格玛因子大肠杆菌Rsd和噬菌体T4 AsiA与大肠杆菌的基本管家西格玛因子sigma（70）结合。虽然已知这两个因素都与sigma的c端区相互作用（70），但这些相互作用的生理后果却非常不同。本研究旨在揭示大肠杆菌Rsd和噬菌体T4 AsiA抑制或调节大肠杆菌RNA聚合酶活性的机制，从而不同程度地抑制大肠杆菌细胞的生长。研究发现，AsiA是更有效的体内转录抑制剂，因此对大肠杆菌细胞生长具有更高的抑制作用。表面等离子体共振实验测量的亲和常数表明，Rsd和AsiA结合到或70具有相似的亲和。体内和体外结合实验的数据清楚地表明，AsiA与Rsd的主要区别在于AsiA与RNA聚合酶形成稳定三元配合物的能力。利用酵母双杂交系统研究了AsiA和Rsd与sigma（70）的结合模式，发现sigma（70）的第4区参与了这两种抗sigma因子的结合；然而，Rsd也与sigma的其他区域相互作用（70）。综上所述，这些结果表明，AsiA表达对大肠杆菌生长的较高抑制作用可能是由于AsiA蛋白捕获全酶RNA聚合酶的能力，而不是其与sigma的较高结合亲和力（70）。
Anti-sigma factors Escherichia coli Rsd and bacteriophage T4 AsiA bind to the essential housekeeping sigma factor, sigma(70), of E. coli. Though both factors are known to interact with the C-terminal region of sigma(70), the physiological consequences of these interactions are very different. This study was undertaken for the purpose of deciphering the mechanisms by which E. coli Rsd and bacteriophage T4 AsiA inhibit or modulate the activity of E. coli RNA polymerase, which leads to the inhibition of E. coli cell growth to different amounts. It was found that AsiA is the more potent inhibitor of in vivo transcription and thus causes higher inhibition of E. coli cell growth. Measurements of affinity constants by surface plasmon resonance experiments showed that Rsd and AsiA bind to or 70 with similar affinity. Data obtained from in vivo and in vitro binding experiments clearly demonstrated that the major difference between AsiA and Rsd is the ability of AsiA to form a stable ternary complex with RNA polymerase. The binding patterns of AsiA and Rsd with sigma(70) studied by using the yeast two-hybrid system revealed that region 4 of sigma(70) is involved in binding to both of these anti-sigma factors; however, Rsd interacts with other regions of sigma(70) as well. Taken together, these results suggest that the higher inhibition of E. coli growth by AsiA expression is probably due to the ability of the AsiA protein to trap the holoenzyme RNA polymerase rather than its higher binding affinity to sigma(70).